This application claims the priority benefit of Japanese application serial no. 2001-288567, filed on Sep. 21, 2001
1. Field of the Invention
This invention relates in general to an image forming device, such as a printer, a facsimile, or a multi-function machine with the above functions. More specifically, the invention relates to an image forming device of electrophotographic type where a toner image formed on an image supporter is transferred by charging, optically writing and developing, and then the image is transferred onto a transfer material, such as a sheet or an intermediate transfer material. The present invention also relates to a developing device for developing a latent image on the image supported in such image forming device.
2. Description of Related Art
Conventionally, referring to FIG. 7, an image forming device of electrophotographic type has a developing device using a dry type two-component developer consisting of carrier and toner. The developer contained in the developing case 1 is scratched by the rotation of the paddle 2 to adhere on the developer supporter 3. As the developer supporter 3 rotates, the developer supported thereon is thinned by a thinning member 4. After being thinned, the developer is adhered to develop an electrostatic latent image on the image supporter 5.
In this developing device, a developer scattering blocking member 6 is disposed at a position adjacent to the downstream side of the thinning member 4 in the developer supporter 3""s rotational direction B. Entrance seals 7, 8 made of polyurethane, etc. are held on the developer scattering blocking member 6, and an opposite surface 9 is formed opposite to the developer supporter 3.
The developer scattering blocking member 6""s opposite surface 9 is receded to a position away from the developer supporter 3""s circumferential surface from the thinning member 4""s tip, in such a manner without touching the developer on the developer supporter after being thinned by the thinning member 4. Therefore, a step portion s is formed at the tip of the thinning member 4""s downstream side in the developer supporter 3""s rotational direction B.
For example, as shown in FIG. 8, the developer adhered on the step portion accumulates as t after long time use. This accumulated t portion gets hard in a short time, and falls on the developer supporter due to impact, etc. This causes a problem such that the image formed on the transfer material is distorted.
In order to solve this problem, for example, as disclosed in Japanese Laid Open No. 5-2340 and No. 5-2341, the magnitude or the polarity of the magnetic force of the developer supporter is changed at the downstream and the upstream sides of the thinning member in the developer supporter""s rotational direction. However, although it is effective for the toner adhesion on the tip of the thinning member, a sufficient effect cannot be achieved for the toner adhesion on the downstream side""s tip or the developer scattering blocking member.
In addition, for example, as disclosed in Japanese Laid Open No. 10-161496, among the napped developer, toner that has small charge amount and contains much paper powder is removed from the napped developer by the centrifugal force caused by the magnetic roller""s rotation. However, as the recycled toner amount at the position near the magnetic roller increases, it is normally very difficult to adhere only the charged toner. Foreign articles such as the paper powder are mixed within the napped developer, so that a sufficient effect cannot be achieved.
According to the foregoing description, the first object of the present invention is that to install a special device such as a paper powder removing device is not required. Without increasing the cost, the toner can be prevented from adhering on the tip of the thinning member""s downstream side, and the adhered toner can be prevented from falling on the developing sleeve 28 and reducing the image quality.
According to the second object of the present invention, the toner can be prevented from accumulating on the tip of the thinning member""s downstream side covered by the developer scattering blocking member. Therefore, the toner adhered thereon can be prevented from falling on the developer supporter and reducing the image quality.
According to the third object of the present invention, the space between the opposite surface and the developer supporter can be maintained. Even though the toner naps, blocking the developer does not occur. Therefore, after thinned by the thinning member, the toner on the developer supporter is not disturbed, so that it is able to provide a good image.
According to the fourth object of the present invention, due to the toner napping, the toner is transported, while the tip of the napped toner is regularly in contact with the opposite surface of the developer scattering blocking member. Therefore, a cleaning effect can be achieved to prevent the toner from adhering, and it can also prevent the adhered toner from falling on the developing sleeve and reducing the image quality.
According to the fifth object of the present invention, an image forming device with the above developing device is provided to achieve the foregoing objects.
Recently, in the image forming device, in view of environmental protection or the reduction of running cost, a recycling device, which is used for recycling the toner that is not transferred to the transfer material, such as the sheet or the intermediate transfer body to return to the developing device, is generally installed.
In such an image forming device, during the transfer stage, the foreign articles, such as the paper powder, adhered on the image supporter or the intermediate transfer body are mixed with the recycled toner. The mixed paper powder is subject to a lot of mechanical stress from the transporting member, etc., and therefore is shivered into tiny powder before the paper powder return to the developing device. The charge amount of the shivered paper powder is small. As the paper powder that has only small charge amount and cannot be held by the carrier gets accumulates more and more with time in the developer, the toner containing a lot of paper powder scatters and accumulates on the step portion s.
In particular, recently, since users use a lot of paper containing large amount of paper powder such as the recycled paper, the toner containing a lot of paper powder scatters and accumulates much more than ever before, and this accumulated toner gets hard in a short time, and falls on the developer supporter due to impact, etc. This causes a problem such that the image formed on the transfer material is distorted.
According to the sixth object of the present invention, even though in the image forming device equipped with a toner recycling device where foreign articles such as the paper powder are mixed and toner adhesion occurs easily, the toner can be prevented from adhering onto the tip of the developing doctor blade""s downstream side or the developer scattering blocking member adjacent to that tip. Therefore, the adhered toner can be prevented from falling on the developing sleeve and reducing the image quality.
According to the objects mentioned above, the present invention provides a developing device, used in an image forming device. In the image forming device, a developer supported on a developer supporter is thinned by a thinning member, and after being thinned, the developer is adhered to develop a latent image on an image supporter. An adjacent member is disposed at a position adjacent to the thinning member""s downstream side in the developer supporter""s moving direction, the adjacent member""s thinning member side of the opposite surface that is opposite to the developer supporter and the tip of the thinning member are disposed with an equal distance from the developer supporter.
In addition, the above developing device can further comprise a developer scattering blocking member, which is used as the adjacent member, disposed to cover the developer supporter to prevent the developer from scattering.
In this developing device, the developer scattering blocking member""s opposite surface is gradually separated from the developer supporter at the downstream side of the developer supporter""s moving direction.
Moreover, the opposite surface is separated from the developer supporter with an equal distance beyond midway of the downstream side of the developer supporter""s moving direction.
Alternatively, the present invention further provides an image device. In this image forming device, the developing device has the aforementioned features.
Furthermore, the above image forming device can further comprise a toner recycling device, for recycling the toner that is not transferred to a transfer material to return to the developing device.